Electrophysiological evidence has been obtained showing that part of the response evoked by a stimulus does not solely depend upon the stimulus, but reflects the release of information about prior events. The proposed research will study the release of readout processes in neuronal systems under various conditions, classifying different types of evoked response modes using a computer. Experiment 1: Modes of response elicited by visual and auditory stimuli will be classfied as cats in a T-maze undergo a variety of learning experiences, acquire a differential response, and undergo reversal of training, transfer to a new stimulus modality, and extinction. The order of appearance and relative latencies of new components or response modes in different structures during training will be catalogued and compared with the release of readout components in subsequent performance. Experiments 2 and 3: The set of anatomical regions displaying readout processes will be identified and the sequence of activation of different structures will be analyzed. Frequencies of different modes will be tabulated and transition probabilities calculated for various sequences of state. Existing data on magnetic tape will be used for these studies. Experiment 4: Chronic and acute microelectrode studies will be carried out to ascertain the neuronal concomitants of readout processes in the evoked potential.